The semiconductor integrated circuit (IC) industry has experienced rapid growth. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC manufacturing are needed. For example, because a trench isolation structure's aspect ratio increases as device technology nodes scale down, filling the trench isolation structure, such as a shallow trench isolation (STI) structure, has become complex and costly. Conventional trench isolation structure profiles and processes for filling the trench isolation structures implement complex and costly combinations of etching, deposition, annealing, and curing processes to achieve adequate filling. Accordingly, although existing trench isolation structure profiles and methods for filling these trench isolation structures have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects.